Adult flies of many species in this family are mimics of bees or wasps. They are mostly black with yellow or orange stripes. A few others are brown, or metallic green or blue (these may also be mimics of bees). They have large eyes and short mouthparts formed into a tube with a sponge at the end. Their bodies may be slim or stout and are sometimes flattened top-to-bottom. Some species wag they abdomens up and down when they land. Like all flies they only have two wings, their hind wings are reduced (see More Information about True Flies for more).
Larvae are more variable. They are all legless and headless, but some aquatic species have long breathing tubes on their hind ends, some have tough skins, some look like little slugs. Color varies from white to brown to green.
This family of flies is found all over the world, and there are thousands of species. Nobody knows exactly how many species there are in Michigan or in the whole Great Lakes region, but it is probably more than 150.
Adult Flower Flies are found (surprise!) around flowers. They are also found near places where their larvae might live and feed and this is variable (see below).
Flower Fly larvae live in many different types of habitats. Some live in still or slow-moving freshwater, some live in decaying wood, some live in dung, some on plants, and some in the nests of other insects.
Flower Flies have complete metamorphosis, see More Information under True Flies for the basic fly life cycle. In cold climates they spend the winter as larvae or pupae.
Most Flower Flies live a year or less, but some aquatic species that live in cold climates may survive as larvae for several years before metamorphosing into adults.
Adult Flower Flies are only active on warm sunny days. Larvae may be active any time. Some species travel long distances, but most stay close to where they grew up. They are always solitary, only coming together for mating. One group of aquatic larvae have evolved a special way of getting air without going to the surface of the water, they have sharp structures on their abdomen that they stab into hollow reeds growing in the water. The reeds have air inside them, and the fly larvae breath that.
These flies find each other by sight, sound, and maybe scent. They have good wide-angle vision to find each other and watch out for predators. They can continue to make vibration noise by moving structures in their thorax even when they are not moving or flapping their wings.
Adult flower flies feed on nectar from flowers and from aphid "honeydew" (see Aphids).
The larvae of different species feed on different kinds of food. Some feed on decaying, damp plant material, on fungi or on green plants, some on the bulbs of plants in the lily family, some in dung. Many are aquatic and live in shallow freshwater (sometimes in water that seems foul and polluted), some in water-filled treeholes. Some species are scavengers in the nests of ants or wasps. Some of the most amazing are predators on slow-moving, soft-skinned insects like aphids. These predators have no eyes and no legs, but they still hunt and eat these little insects.
Adult flower flies rely on their high-speed flight and their similarity to stinging insects to avoid or discourage many predators. Larvae hide in muck and mud, and some live only in small treeholes where there are not very many predators. The species that live in nests of ants and wasps have adjusted their scent so they don't smell like food, and they stay out of the way of the other insects as much as they can.
Flower Flies are imporant pollinators of many flowers. Their larvae help clean up and break down dead plants, and feed on micro-organisms.
A few species of Flower Flies have larvae that damage bulbs or green plants that are valuable to humans. They are not a major agricultural pest, but they do sometimes cause damage.
These flies can be important pollinators, and some species feed on aphids that are pests.
No Flower Fly species are currently known to be endangered in the United States, but some species in other countries are considered endangered and at risk of extinction.